Can I use Blender on Intel HD 530 dedicating an Nvidia GPU to Cycles?
You can definitely do this. My son has an Ubuntu Desktop:
$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=20.04
DISTRIB_CODENAME=focal
DISTRIB_DESCRIPTION=&quot;Ubuntu 20.04.2 LTS&quot;

And this graphics card specifically:
$ lshw -c video
  *-display
       description: VGA compatible controller
       product: HD Graphics 530
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 06
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:134 memory:f6000000-f6ffffff memory:e0000000-efffffff ioport:f000(size=64) memory:c0000-dffff

He's able to render cars for NR2003 using this setup.

NOTE: The render times can be long he constantly lets me know that they can take 1-2hrs but it is doable.
CPU Info
Here's his CPU info too just in case.
$ lscpu
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   39 bits physical, 48 bits virtual
CPU(s):                          4
On-line CPU(s) list:             0-3
Thread(s) per core:              2
Core(s) per socket:              2
Socket(s):                       1
NUMA node(s):                    1
Vendor ID:                       GenuineIntel
CPU family:                      6
Model:                           94
Model name:                      Intel(R) Core(TM) i3-6100 CPU @ 3.70GHz
Stepping:                        3
CPU MHz:                         800.052
CPU max MHz:                     3700.0000
CPU min MHz:                     800.0000
BogoMIPS:                        7399.70
Virtualization:                  VT-x
L1d cache:                       64 KiB
L1i cache:                       64 KiB
L2 cache:                        512 KiB
L3 cache:                        3 MiB
NUMA node0 CPU(s):               0-3